The present invention refers to a tool for forming material bodies, e.g., by compacting powder, preferably using a high velocity compacting (HVC) method, wherein a punch acting to shape and compact the material in a die is subjected to a series of very short-timed and very powerful impacts with velocities above approximately 1 m/s, and preferably over 2 m/s.
In conventional press tools the upper punch is fixedly mounted on the unit delivering the pressing force into the tool. Such an arrangement, however, is generally not suitable for high velocity compacting, as tests have shown that any component which has been mounted directly on the impact plunge will break down within a very short period of time due to the intense and repeated impacts to which the compacting tool is subjected during the high velocity compacting.
Accordingly, there exists a need for a tool suitable for high velocity compacting where, on one hand, the upper punch is not mounted directly on the impact plunge and which, on the other hand, does not interfere with charging of the compacting cavity with powder material or the like.
The purpose of the present invention is therefore to provide a forming or compacting tool in which the above-described problem has been eliminated. The present invention achieves this goal by providing a forming tool having a die with a seat for receiving a material to be formed, an upper punch axially movable into and out of the seat from one side of the die, a lower punch axially movable into and out of the seat from the opposite side of the die, movable loading means for introduction of the material into the seat, an impact press arranged to subject the upper punch to a series of compacting impacts, a unit for supplying a driving force to the tool, and a control device for controlling the motion of the movable parts of the tool. The forming tool further includes an impact head positioned above the die and supporting the upper punch. The impact head is arranged to receive the compacting impacts delivered by the impact press. Further, the impact head is guided and centered in a position aligned with the seat in the die by a vertically adjustable roof supported in a tool housing. The impact head is thereby mechanically disengaged from the roof for substantially preventing impact forces from propagating into the tool housing.
According to a further aspect of the present invention, the roof is provided with a center aperture through which the impact head extends. The roof aperture has a lower mechanical stop and an upper mechanical stop which are spaced apart in an axial direction. The impact head has an external flange of a height less than a distance between the two mechanical stops of the roof, and the flange has a predetermined size which prevents movement of the flange below the lower mechanical stop and above the upper mechanical stop. The flange is thus positioned during impacts between the upper and lower mechanical stops.
A further aspect of the present invention is directed to an improvement in a forming tool comprising a die with a seat for receiving a material to be formed, an upper punch axially movable into and out of the seat from one side of the die, a lower punch axially movable into and out of the seat from the opposite side of the die, and an impact press arranged to subject the upper punch to a series of compacting impacts. The improvement of the present invention comprises an impact head positioned above the die and supporting the upper punch, with the impact head being arranged to receive the compacting impacts delivered by the impact press. The impact head is guided and centered in a position aligned with the seat in the die by a vertically adjustable roof supported in a tool housing. Moreover, the impact head is mechanically disengaged from the roof for substantially preventing impact forces from propagating into the tool housing. In a preferred embodiment of the present invention, the impact head further includes a projecting flange and the roof includes an upper mechanical stop and a lower mechanical stop. The flange of the impact head is retained between the upper and lower mechanical stops; however, when the upper punch is subjected to the series of compacting impacts, the flange does not contact the upper and lower mechanical stops. Thus, propagation of the impact forces is prevented.
Still further, another aspect of the present invention provides an impact head arrangement for supporting an upper punch in a forming tool. The arrangement comprises an impact head and a vertically adjustable roof for guiding and centering said impact head, wherein the impact head is mechanically disengaged from the roof during compacting impacts such that impact forces are substantially prevented from propagating to the forming tool. In a preferred embodiment of the present invention, the impact head further includes a projecting flange and the roof includes an upper mechanical stop and a lower mechanical stop, with the flange of the impact head being retained between the upper and lower mechanical stops. When the upper punch is subjected to a series of compacting impacts, however, the flange does not contact the upper and lower mechanical stops of the roof and propagation of the impact forces to the forming tool is thereby substantially prevented.